In turbines or compressors, in particular in gas turbines, movable turbine parts, such as rotor blades in a compressor stage or in a turbine stage, rotate with a high rotary speed around a turbine shaft. In order to prevent an unbalance during rotation, balancing weights have to be placed to the movable turbine parts for balancing the movable parts. An unbalance of the movable turbine parts leads to damages of the turbine, e.g. in the bearings, and thus to higher maintenance costs.
In order to balance the movable parts of the turbine, the balance weights are fixed to the movable turbine parts in a balanced position. In the balance position, the balancing weights are permanently fixed, so that an undesired displacement of the balancing weights during operation of the turbine is prevented.
Conventional designs of movable turbine parts, such as turbine discs, comprise a number of holes that are equispaced axially or radially in the turbine disc or in a shaft of a turbine, wherein into the holes fixing elements for locking the balance weights are insertable.
U.S. Pat. No. 6,640,704 B2 discloses a device for providing a balancing of rotating bodies, in particular for balancing a drum of a roller of a printing plate exposure device. A weight element is placed in a T-Slot of a movable part and is fixed by a pin in order to prevent a further displacement.
EP 1 052 424 B1 discloses an apparatus for balancing turbine rotors. A balancing weight is fixed to a movable turbine part and is fixed by a threaded fastener that is screwed in a threaded hole of the balancing weight element.
U.S. Pat. No. 4,842,485 discloses a movable turbine part, such as a turbine rotor, wherein an expandable weight assembly is fixed to the movable part. An expander screw expands the cross-section of the weight assembly in order to press the weight assembly at a desired position in a groove of the movable part.
U.S. Pat. No. 3,736,811 discloses a balance weight attachment for a movable part of turbines. A split weight construction comprises a body portion capable of being mounted in a groove of the movable part. The body portion comprises a threaded oblique passage way, so that a screw may pass there through so as to bear the body part against the other side of the groove, when the screw is tightened. Thus, the body portion is fixed at a desired position of the movable part.
U.S. Pat. No. 5,285,700 A discloses a method for balancing a rotor portion of a gas turbine engine. A bolt for connecting two movable parts of the turbine carries a set screw which comprises a balancing weight in order to balance the movable parts.
US 2006/0053882 A1 discloses an apparatus for balancing a gas turbine engine. Balancing washers are attached to a bolt that connects movable turbine parts in order to balance the movable parts.
US 2002/0029653 A1 discloses a balancing weight for a rotary component in a turbo machinery. A balancing weight is attacked to a groove of the rotary component. By a central opening in the balancing weight a tool for controlling, i.e. fixing and adjusting the balancing weight, is receivable.
U.S. Pat. No. 3,916,495 discloses means for balancing a gas turbine engine, with which two movable parts of a turbine may be removed and replaced without performing an additional balancing operation. A tie bolt fixes the two movable turbine parts, wherein the tie bolt comprises balancing washers in order to balance the movable turbine parts.